poj Drainage Ditches

模版题，很多人A.模版： http://blog.csdn.net/rookie_algo/article/details/7803313

#include<iostream>
using namespace std;
const int inf = 0x7fffffff;
const int MAXN = 210;
const int MAXM = MAXN*MAXN;
int map[MAXN][MAXN];
int dis[MAXN];
int queue[MAXM];
int bef[MAXN];
int num[MAXN];
void set_dis(int end)
{
	int top(0),base(0);
	memset(dis,-1,sizeof(dis));
	memset(num,0,sizeof(num));
	queue[top++] = end;
	dis[end]=0;num[0] = 1;
	while(top!=base)
	{
		int pre = queue[base++];
		for(int i=end-1;i!=0;i--)
		{
			if(dis[i] != -1 || map[i][pre] == 0)
				continue;
			dis[i] = dis[pre]+1;
			queue[top++] = i;
			num[dis[i]]++;
		}
	}
}
int cmp(int x,int y)
{
	if(x<y)
		return x;
	return y;
}
int remark(int n,int a)
{
	int tmp=inf;
    for(int i=1;i!=n+1;i++)
		if(map[a][i]!=0&&dis[i]>=0)
			tmp=cmp(tmp,dis[i]+1);
    if(tmp==inf)
		tmp=n;
    return tmp;
}
int SAP(int n,int s)
{
	int j,a = s;int flow(0);
	memset(bef,-1,sizeof(bef));
	while(dis[s]<n)
	{
		for(j=1;j!=n+1;j++)
		{
			if(map[a][j]>0&&dis[a]-1==dis[j])
			{
				break;
			}
		}
		if(j<=n)
		{
			bef[j] = a;a = j;
			if(a==n)
			{
				int i = n,max(inf);
				while(bef[i]!=-1)
				{
					max = cmp(max,map[bef[i]][i]);
					i = bef[i];
				}
				i = n;
				while(bef[i]!=-1)
				{
					map[bef[i]][i]-=max;
					map[i][bef[i]]+=max;
					i = bef[i];
				}
				flow+=max;a=s;
			}
		}
		else
		{
			int x = remark(n,a);
			num[x]++;num[dis[a]]--;
            if(num[dis[a]]==0)
				return flow;//间隙优化 gap
            dis[a]=x;
            if(a!=s)
				a=bef[a]; 
		}
	}
	return flow;	
}
int main()
{
	int e,n;
	//cout<<inf<<endl;
	while(cin>>e>>n)
	{
		memset(map,0,sizeof(map));
		while(e--)
		{
			int a,b,w;
			cin>>a>>b>>w;
			map[a][b] += w;
		}
		set_dis(n);
		cout<<SAP(n,1)<<endl;
	}
	return 0;
}